code: def get_size(self):
      return sys.getsizeof(self._string.getvalue())
  
file_path: FATE/python/fate/arch/federation/message_queue/_datastream.py
imports: import io
  import json
  import sys
label_desc: Use image node_id 2 for calling the Datastream obj's underlying member method code with example usage: obj.get_size() and returns: sys